1. Field of the Invention
The present invention relates generally to toner cartridge systems, such as used in laser printers and the like, and, more particularly, to a toner adder brush roller and method for controlled installation of a brush filament population on a shaft of a toner adder brush roller.
2. Description of the Related Art
A toner adder roller, also know as a toner supply roller, is the first item of hardware that toner encounters in a conventional laser printer toner cartridge. The toner adder roller is made from a conductive foam which is compressed against a harder developer roller. The developer roller and toner adder roller rotate and form a nip between one another. The role of the toner adder roller in the cartridge is two-fold: as a first mechanism, applying fresh toner onto the developer roller; and, as a second mechanism, removing old toner from the developer roller surface. Both mechanisms have electrostatic charge and mechanical attributes.
The toner adder roller has been identified as one factor contributing to toner starvation in toner cartridges which ultimately leads to failure of a laser printer toner cartridge system. One theory is that starvation occurs when the toner adder roller cannot sufficiently supply the developer roller with fresh toner.
The toner starvation issue continues to pose a substantial problem and is only likely to become more pressing in view of the future need in the market for higher print speeds and for cartridges that have longer print life. The increased torque generated at higher speeds in combination with a longer cartridge life will only increase the toner starvation issue. In addition, the faster print speeds will require more strain on the power train and will also generate more heat in the cartridge. All these effects mentioned above are expected to have negative impact on the print quality and to the cartridge itself.
An alternative toner adding hardware item has been proposed in the past, a toner adder brush roller, also known as a toner supply brush roller. U.S. Pat. No. 4,083,326 discloses an “electrically conductive fur brush” roller loaded with brush materials made of natural and synthetic fibers, and also made of fibers extruded and containing conductive particles such as carbon. Thus, instead of attaching a conductive foam cylinder onto a shaft as done in making the toner adder roller, a toner adder brush roller may be made by loading and adhering conductive filaments or fibers perpendicularly to the shaft. This can be done by two processes: wrapping a woven ‘velvet’ strip around the shaft or fixating the filaments directly onto the shaft through a flocculation process.
The toner adder brush roller possesses a number of characteristics that make it appear to be a potential solution to the toner starvation problem encountered by the toner adder roller. The softer nature of the filaments noticeably reduces the torque in the toner adder brush roller/developer roller nip, compared to a system utilizing the toner adder roller. The greatly increased surface area also has the potential to improve the capability of the toner adder brush roller to charge triboelectrically compared to the toner adder roller, since triboelectric charge is a surface phenomenon.
However, the flocked and the woven toner adder brush roller each possess a unique set of characteristics that may lead either to severe print quality defects or to system failure. In the case of the flocked toner adder brush roller and depending on the toner, the toner that ends up between the densely populated toner adder brush roller filaments cannot get back out. Consequently, toner packing occurs with the result that the flocked toner adder brush roller is essentially transformed into a solid cylinder. In the case of the woven toner adder brush roller, wherein a woven fabric is cut into bands and wrapped around and adhered to the shaft in a spiral configuration, wrap pattern print defects occur as a function of the gap formed between the fabric edges. Thus, there is a need to find a toner adder brush configuration that combines the wanted characteristics of each existing version while eliminating the properties that cause problems.
As a result, there is a need for an innovation that will overcome the above-mentioned defects for providing a solution to the toner starvation problem encountered by laser printer toner cartridge systems.